Exim maintainers have warned of an in-the-wild attack that allowed the miscreants to execute malicious code with unfettered system privileges by exploiting a bug in older versions of the open-source mail transfer agent.

The memory-corruption vulnerability resides in Exim 4.69 and earlier versions, and already has been used in at least one attack to completely root an enterprise server, according to this account. Security pros have sounded the alarm because the vulnerability is remotely exploitable and is already being used maliciously. What's more, attack code has also been added to the Metasploit exploitation kit, making it easy for others to reproduce the attack.

__________________
You don't need to be a genius to debug a pf.conf firewall ruleset, you just need the guts to run tcpdump